THE LAW OF EVOLUTION 



equivalents. Why this apparent excess of car- 

 bon ? The answer is to be found in the fact 

 that nitrogen, unlike most other substances, ab- 

 sorbs heat on entering into combination. To 

 the molecular motion which keeps it when free 

 in a gaseous state, it adds a vast quantity of 

 molecular motion. It has been calculated that 

 the union of a pound of oxygen with nitrogen, 

 in forming nitrous oxide, is attended by the ab- 

 sorption of enough heat to raise the tempera- 

 ture of 9232 pounds of water one degree Cen- 

 tigrade. It is probably owing to this peculiarity 

 that nitrogen, which is so inert when free, is 

 so wonderfully active when combined. Hence, 

 too, we may understand the extreme instability 

 of such nitrogenous substances as gunpowder, 

 gun-cotton, and nitro-glycerine. And hence we 

 may begin to discern the reason why nitrogen 

 is the most important of the chemical elements 

 concerned in maintaining vital activity. Now 

 when we compare this property of nitrogen 

 with the apparent excess of carbon in the albu- 

 men-molecule, we may fairly surmise that the 

 two facts indicate a balance between the forces 

 that tend to produce internal rearrangement and 

 the forces that tend to prevent disintegration. 



Fifthly , besides the fact that organic bodies 



usually possess an amount of heat which keeps 



their temperature somewhat above that of their 



inorganic environment, we have to note the fact 



215 



